The imprinting method is a method for forming patterns corresponding to a pattern of a mold on a substrate. The patterns are formed by pressing the mold, on which a pattern has been formed in the shapes of protrusions and recesses in advance, against a resist resin layer of a processing target substrate. The imprinting method is gathering attention in the fields of semiconductor elements and patterned media such as hard disks that require refinement, from the viewpoints of formability of fine patterns, productivity, and cost.
Representative techniques of the imprinting method include a thermal imprinting method, a thermal embossing method, and an optical imprinting method. In the thermal imprinting method, a thermoplastic resin is employed as resist, a mold is pressed against the resist at high pressure in a temperature range in the vicinity of the Tg of the resist, then the mold is separated from the resist after the temperature is lowered to Tg or less to solidify the shapes of a pattern. The thermal embossing method also employs a thermoplastic resin as resist. In the thermal embossing method, a mold is pressed against the resist at high pressure in a temperature range lower than Tg, to form a pattern. In the optical imprinting method, a resist which is liquid and has fluidity at room temperature is cured by photocuring in a state in which a mold is pressed against the resist, to transfer a pattern.
From among the above techniques, there are expectations for optical imprinting method as a next generating fine processing production technique which is capable of forming highly precise patterns using molds having desired patterns thereon easily and at low cost. There are expectations for the optical imprinting method as a technique which is a process that can be executed at room temperature as opposed to the thermal methods and does not require high pressure, while also capable of refinement and reduction of residual film thickness corresponding to the thickness between the recesses of patterns and substrates.
Favorable mold release properties, thinness and in plane uniformity of resist layers between the recesses of patterns and substrates (residual film thickness), and etching resistance of resist material during following lithography processes are required in optical imprinting in order to perform patterning with high quality rectangular pattern shaping properties and roughness.
Patent Documents 1 and 2 disclose imprinting resist having fluorine resin as a main component. Favorable mold release properties are secured by using fluorine resin as a main component of the resist.
Patent Document 3 discloses a technique that improves mold release properties by causing a fluorine containing layer to be present on the surface of a resist layer. Patent Document 4 discloses a technique that improves the wetting properties of a resist material with respect to a mold and mold release properties, by employing a resist composition that includes a surfactant as expelled liquid, arranging resist in a specific pattern of discrete droplets, and causing a large amount of a surfactant to adhere to locations on the surface of the mold corresponding to the droplet arrangement pattern.